1. Field of the Invention
The present invention relates to an optical device manufacturing method of dividing an optical device wafer into a plurality of optical devices sectioned along streets and joining a heat sink to each of the optical devices, the optical device wafer being formed with the optical devices in an optical device layer lying on the front surface of a substrate.
2. Description of the Related Art
In the optical device manufacturing step, a plurality of optical devices are formed in an optical device layer made of a gallium nitride-based compound semiconductor or the like on the front surface of a sapphire substrate, a silicon carbide substrate or the like. An optical device wafer formed with the optical devices in the optical device layer as mentioned above is divided into the individual optical devices sectioned along streets for manufacture.
As a method of dividing an optical device wafer along streets, a method is proposed in which a laser beam capable of passing through an optical device wafer is directed along a street to form a laser-processed groove and external force is applied along the laser-processed groove to split the wafer. See e.g. Japanese Patent Laid-open No. Hei 10-305420. On the other hand, since an optical device produces heat, a heat sink member is joined to the optical device in order to dissipate the heat. See e.g. Japanese Patent Laid-open No. Sho 60-92686.
An optical device is formed e.g. 0.3×0.3 mm square. It is troublesome to join each heat sink to such a small optical device, which poses a problem of poor productivity. It may be intended that a heat sink material having a size corresponding to that of an optical device wafer is joined to the front surface of an optical device layer and a laser beam is directed along a street formed on the optical device wafer to cut the heat sink material along with an optical device wafer. However, since the heat resulting from the energy of the laser beam escapes through the heat sink material made of metal such as copper, the heat sink material cannot be cut.
Alternatively, it may be intended that a heat sink material having a size corresponding to an optical device wafer is joined to the front surface of an optical device layer and the heat sink material together with the optical device wafer is cut along streets formed on the optical device wafer by a cutting blade. Even such a case, it is difficult to simultaneously cut the high-brittle optical device wafer and the heat sink material made of metal such as high-ductile copper.